It is essential to provide a continued and adequate supply of great apes, particularly chimpanzees, for appropriate biomedical research into human health-related problems for which they are the only applicable models. The overall goals of this project is to continue to develop artificial breeding of chimpanzees (Pan troglodytes) as an effective means of increasing the birth rate at facilities in the United States which house these animals. Four specific goals will be achieved: 1. IMPROVEMENT OF THE SUCCESS OF ARTIFICIAL INSEMINATION BY DEVELOPMENT OF METHODS FOR INDUCTION OF MULTIPLE OVULATION AT A SPECIFIC TIME. Induction of "moderate" superfolliculation will result in the ovulation of a limited number of oocytes over a more prolonged period of time that is the case in spontaneous ovulation and results in an increase in pregnancy rate, without undue increase in multiple pregnancies. 2. IDENTIFICATION OF PHYSICAL CORRELATES OF OVULATION (EXTERNAL MARKERS) SUITABLE FOR USE IN ANIMAL MANAGEMENT. Although routine monitoring of perineal selling has been assumed to provide adequate indication of "normal" menstrual cyclicity, data recently too hand suggests that a refined version of such monitoring can identify potentially infertile cycles in otherwise normal animals. 3. IMPROVEMENT OF FREEZE METHODS FOR SPERM. A method has recently been developed for freezing of chimpanzee sperm which has provided thawed samples which initiated two chimpanzee pregnancies. The method is less than optimal, and continued research is needed to improve the results. 4. MAINTENANCE OF A FROZEN SEMEN BANK. Funds are requested to continue maintenance of a sperm bank for semen of great apes, using sperm collected and frozen using methods demonstrated to be compatible with maintained fertilizing capacity. Once developed and ongoing, this artificial breeding program will be relatively inexpensive to maintain; provide additional knowledge regarding the reproductive physiology of the great apes; and be adaptable to other colonies. The integrity of the species will be assisted by maintenance of genetic diversity.